1. Find of the Invention
The device relates to an electrode device, for intracardiac stimulation and/or defibrillation of heart tissue and/or sensing heart signals in a patient, of the type having a soft, flexible electrode cable with an outer coating of insulation containing at least one elongate conductor connected to an electrode arranged on the electrode cable.
2. Description of the Prior Art
With the aid of e.g. a bipolar pacemaker electrode device, the heart can be stimulated and its activity sensed with the electrodes arranged on the electrode cable. For good sensing of heart activity and desired stimulation of the heart, it would be very advantageous if the electrodes pressed against the heart wall. Maintaining electrode contact with cardiac tissue is possible with the use of fixing means which, virtually without exception in the art, are arranged only near the electrode located at the distal end of the electrode cable. The other electrodes on the electrode cable are floatingly arranged in the heart.
A fixing means of this kind, which consists of backwardly pointing tines, is known from U.S. Pat. No. 4,409,994. The tines are caused to become embedded in the heart's trabeculae and will accordingly keep the electrode pressed against the heart wall. Tines of this kind, however, could penetrate into heart tissue, thereby damaging the myocardium. Another way to have the electrode press against the heart wall and which is non-traumatic is to use a relatively heavy electrode head, as is described in U.S. Pat. No. 3,911,928. Another electrode device using non-traumatic, a basket-shaped fixing means is known through U.S. Pat. No. 3,935,864. The basket-shaped means, which also serves as the electrode head, ultimately becomes ingrown with tissue and therefore affixed to the wall.
The electrode cable for both these electrodes has a round cross-section. As a result of this shape, the distal electrode head also has a round shape, for the most part, so the arranged conductive surface is usually equally distributed on the electrode head, or the entire surface is conductive. This distribution of the conductive surface is because the cable can rotate on its longitudinal axis. The physician can therefore place the electrode head against the heart wall during implantation, so at least some conductive surface presses against that wall. Since parts of the conductive surface are not in contact with heart wall for stimulation, energy consumption could be needlessly heavy. As a rule, other electrodes arranged on the electrode cable also extend around the electrode cable, leading to the same problem, especially if these electrodes are used for stimulation. As previously noted, the shape of the electrode cable does not generally allow the electrodes arranged behind the distally located electrode to press against the heart wall. The other electrode(s) is/are floatingly arranged in the heart. One example of this is disclosed in the German Patent 3 152 963.
European Application 0 009 732 describes another pacemaker electrode device. In this device, in order for the atrial electrodes to press against surrounding heart wall, one section of the electrode cable is provided with branches forming a basket, these branches being equipped with electrodes. As a result of this construction, such an electrode device is complex and accordingly relatively expensive. It may also be hard to implant.
German Patent 3 912 377 describes a defibrillation electrode device having an elongate electrode cable with a round cross-section which is pre-shaped in such a way that it is helical in the unstretched position, thereby forming a patch-type electrode device. The electrode cable is equipped with a number of adjacent, Outwardly-pointing, wing-like, electrically conductive parts to facilitate the positioning of the defibrillation electrode, in its helical configuration, on the round electrode cable against the external wall of a patient's heart. As a result of these parts, this defibrillation electrode device has a relatively complex structure and is therefore expensive to make.